1. Field of the Invention
This invention relates to a pulsating powder feeder and particularly to a powder feeder employing an indexing system for intermittently positioning powder metering chambers and ejecting reproducible amounts of a powder therefrom.
2. State of the Art
Numerous types of devices have been disclosed in the prior art for despensing powder on a continuous or intermittent basis. In most cases the devices disclosed dispense a continuous flow of powder for use in spraying or coating operations. However, recently several patents have been issued which disclose a device for intermittently dispensing reproducible quanta of powder on a substrate. For example, U.S. Pat. No. 3,909,068 discloses a device employing a series of discs whereby one of the discs contains a number of ports designed to hold reproducible quanta of powder. Another series of ports, on the same disc, direct intermittent pulses of a pressurized gas into the powder ports forcing the powder outwardly through a nozzled outlet.
U.S. Pat. No. 3,913,795 discloses a powder metering device having pulsating characteristics similar to that described above. However, functionally it is distinguishable as it contains an open ended metering chamber specifically designed to move reciprocatably through a powder reservoir. As the metering chamber moves therethrough it is filled with powder and during its reciprocating movement comes into sealed contact with a normally closed opening. A pulse of pressurized gas is then introduced into the other end of the metering chamber causing the normally closed outlet to open and thereby force the powder collected within the chamber outwardly through a nozzled outlet.
Although the above devices have been found to be successful for most types of coating operations, it has now been found that the efficiency and reproducibility of the powder ejection process can be substantially increased if the rotating discs or the reciprocating piston of the prior art devices are replaced by a flexible rotor containing open ended metering chambers and if intermittent movement of the rotor wheel is accomplished by means of a specially designed indexing motor.